This invention relates to compounds that are myeloperoxidase inhibitors, pharmaceutical compositions containing such inhibitors and the use of such inhibitors to treat for example, cardiovascular conditions including acute coronary syndrome.
Myeloperoxidase (MPO) is a heme-containing enzyme belonging to the peroxidase superfamily. Examples of animal peroxidases are lactoperoxidase, thyroid peroxidase, eosinophile peroxidase and myeloperoxidase. Myeloperoxidase is present in primary granules of neutrophils and to a lesser extent in monocytes. It catalyzes the synthesis of hypochlorous acid from chloride and hydrogen peroxide. The hypochlorous acid formed is a powerful oxidant that reacts with a variety of cellular substrates including heme proteins, porphyrins, thiols, iron sulfur centers, nucleotides, DNA, unsaturated lipids, amines and amino acids.
In addition, MPO-catalyzed reactions and their products have been found to exhibit pro-atherogenic biological activity during the development of atherosclerosis and cardiovascular disease. For example, the myeloperoxidase plasma content is correlated with the appearance of cardiovascular disorders in patients suffering unstable angina pectoris. Myeloperoxidase has been reported to contribute to the development of atherosclerosis by the oxidation of lipid and protein in LDL and HDL.
Furthermore, it has been observed that MPO-generated oxidants reduce the bioavailability of nitric oxide, an important vasodilator. Accordingly, high MPO plasma levels are inversely correlated with the success of therapy to establish reperfusion of occluded arteries. High MPO levels are also associated with decreased survival from congestive heart failure. Additionally, it has been shown that MPO plays a role in plaque destabilization which leads to plaque rupture and myocardial infarction.
Therefore, MPO is thought to play a role in several processes that lead to cardiovascular disease including 1) impaired cholesterol trafficking and progession of the atherosclerotic plaque towards an unstable state, 2) destabilization of the atherosclerotic plaque and plaque rupture, 3) consumption of nitric oxide leading to impaired endothelial function and flow, and 4) pathological tissue damage post ischemia contributing to atrial fibrillation and adverse cardiac remodeling with left ventricular hypertrophy leading to congestive heart failure. As such inhibitors of MPO activity are proposed to offer significant therapeutic benefit in the prevention and treatment of cardiovascular disease.
Nevertheless, although MPO has been implicated extensively in the etiology and progression of cardiovascular disease, a biologically safe and non-toxic inhibitor of MPO has yet to be developed. Accordingly, there remains a need for pharmaceutical agents that have myeloperoxidase inhibiting activity and are useful in the treatment, prevention or diminution of the manifestations of the maladies described herein.